Power train assembly

Details Power train assembly Power train assembly

2002-04-17

2004-04-13

Parekh, Ankur (Department: 3681)

Planetary gear transmission systems or components

Differential planetary gearing

Differential or nondifferential planetary combined with...

C475S206000, C180S248000

Reexamination Certificate

active

06719660

ABSTRACT:

BACKGROUND
1. Field of the Invention
The present invention generally relates to motor vehicle power train assemblies. More specifically, the present invention relates to an all wheel drive power train assembly.
2. Description of the Prior Art
Historically, automobiles in the United States have primarily utilized rear wheel drive power delivery schemes. In adapting these rear wheel drive schemes into four wheel drive applications, a transfer case was, and often still is, positioned at the output of the transmission assembly. When engaged, the transfer case diverts a portion of the power coming from the transmission assembly from the rear wheels to the front wheels.
Today, a significant portion of new automobiles in the United States, and perhaps the world, are front wheel drive based vehicles. In a typical front wheel drive vehicle, typically both the engine and the transmission assembly are transversely oriented relative to the vehicle. By positioning the engine and transmission assembly transversely in the vehicle, a more direct coupling of the transmission assembly to the vehicle's transaxle and front wheels is achieved. In doing so, the final drive unit (where the last torque multiplication takes place) and the front wheel differential are often incorporated directly into the transmission assembly itself.
With front wheel drive vehicles themselves becoming a mature market, a recent trend in the automobile industry has been to adapt front wheel drive schemes for all or four wheel drive applications. This is accomplished by providing a power transfer unit that diverts a portion of the power from the front wheels to a rear wheel drive shaft and, subsequently, the rear wheels.
Seen in
FIGS. 1
a
and
1
b
is a typical prior art power transfer unit
10
. The power transfer unit
10
includes a housing
12
within which is located a gear set
14
comprised of a parallel gear set
16
and a non-parallel gear set
18
. The parallel gear set
16
includes a cylindrical extension
20
that operates as its input and this input
20
is coupled to the transversely oriented output
22
of the transmission assembly by way of a splined engagement
24
. The cylindrical extension
20
is off of a gear wheel
26
or may be a sleeve to which the gear wheel
26
mounts. From the gear wheel
26
, power is transferred through a second and third gear wheel, respectively
32
and
34
. These gear wheels
32
and
34
are each supported on bearings
36
for rotation about axes
38
and
40
that are parallel to the rotational axis
28
of the first gear wheel
26
.
The non-parallel gear set
18
includes a bevel ring gear
44
that is mounted to a shaft or sleeve
42
onto which the third wheel gear
34
is mounted or formed therewith. The bevel ring gear
44
engages a bevel pinion gear
46
mounted to another shaft
48
whose axis is generally perpendicular (and therefore non-parallel) to that of shaft
42
. Mounted to an opposing end of the shaft
48
is an output member
50
, illustrated as including a flange
52
and appropriately located bolt openings
54
. The latter features enable the output member
50
to be bolted to a rear drive shaft (not shown).
As seen in
FIG. 1
a,
the line
56
along which the gear wheels
26
,
32
and
34
of the parallel gear set
16
engage with one another generally corresponds with the axis about which the output member
50
rotates. When locating of the power transfer unit
10
relative to the output of the transmission
22
, this line
56
may be offset from the centerline of the vehicle. Additionally and as seen in
FIG. 1
b,
the axis
28
of input into the power transfer unit
10
, is offset, vertically or elevationally in the vehicle, relative to the output axis
58
about which the output member
50
rotates. This “drop” or height decrease from the transmission assembly output
22
to the output member
50
results from the relative positioning of the first, second and third helical gears
26
,
32
and
34
of the parallel gear set
16
, in conjunction with the non-parallel gear set
18
. The non-parallel gear set
18
is a hypoid beveled gear set where the axis of rotation
40
of the bevel ring gear
44
does not intersect the axis
58
of rotation of the bevel gear
46
.
Located within the transmission assembly, and before the output
22
thereof, is a final drive unit (illustrated schematically as box
57
). The final drive unit
57
performs the last torque multiplication in the power train and is configured in any one of a number of conventional constructions well known in the art. One such construction is a planetary gear set with the input to the final drive unit
57
being through a sun gear while the output of the final drive assembly
57
is through a ring gear. The ring gear may be directly coupled to the transmission output
22
and therefore a large amount of torque is delivered to the power transfer unit
10
.
Since the power transfer unit
10
receives power after the final drive assembly
57
, the components of the power transfer unit
10
must be robust enough for high torque loads to pass therethrough. This adds size, weight and expense to the power transfer unit
10
.
In view of the above and other limitations on the prior art, it is an object of the present invention to provide a drive train construction that permits a simpler design of various components, a decrease in the weight of the drive train, a compact construction and a limited amount of power transferred to the rear wheels.
SUMMARY OF THE INVENTION
In overcoming the above and other limitations on the prior art, a power train embodying the principles of the present invention is provided with intermediate output of a transmission that delivers power from the engine to a center differential (a planetary gear differential), which splits and transfers torque to the front wheels and the rear wheels of the vehicle. Through utilization of the power flow scheme of the present invention, it will readily be seen that the power transfer unit can be utilized on the transaxle before the final drive assembly. This allows the power transfer unit's components to be smaller, lighter and simpler in design.
In transferring torque to the front wheels, the sun gear of the center differential causes rotation of a sleeve, which in turn is the input into a planetary gear, final drive unit. The final drive unit multiplies the torque and transfers power to the front differential, which is illustrated as a bevel differential. Thereafter power is provided to the half shafts and subsequently to the front wheels.
In transferring torque to the rear wheels, another sleeve, coupled to the carrier of the center differential, operates as the input member for the power transfer unit and is splined to the input gear wheel of the parallel gear set. A gear wheel, chain, belt or other feature connects the input gear wheel to an output gear wheel of the parallel gear set which is integrally formed with a sleeve or splined to a shaft. The sleeve or shaft operates as the output of the parallel gear set and is connected to the input of a non-parallel gear set.
In the non-parallel gear set, power is generally transferred via the sleeve or shaft to a set of bevel gears and specifically from an input or first axis to a second axis that is non-parallel to the input axis. This transfer of power is effectuated by a first bevel gear mounted or integrally formed on an opposite end of the sleeve or shaft to which the output gear wheel is mounted. A second bevel gear (engaging the first bevel gear) is mounted to a shaft, or integrally formed with the shaft, and operates as the output of the non-parallel gear set. Finally, an output member coupled to the shaft transfers power to the rear wheel drive shaft from the non-parallel gear set.
Simultaneous with the transfer of power to the power transfer unit and the rear wheels, power from the center differential is transferred in parallel to a biasing or torque limiting device. This device is coupled to the input gear wheel of the power transfer unit and operates so as

Affiliated with

Also associated with

Rating

Power train assembly does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Power train assembly, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Power train assembly will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3246465